Efficient structured data processing for web service enabled shop floor devices

State of the art factory automation systems are now using Service Oriented Architecture (SOA) in order to increase flexibility and lower complexity of process monitoring and control. However, the service technology has not yet penetrated into the lower levels of plant-wide automation processes i.e. throughout shop floor devices such as programmable controllers, embedded sensors and actuators. Different techniques to adapt the web service technology to the specific requirements of embedded systems domain are intensively investigated by researchers and yet real-time properties, limited resources and wireless links are still posing immense challenges. The most promising solutions proposed are based on a newly emerging structured data format - Efficient XML Interchange (EXI). It is designed to compensate for the inefficiency of widely used throughout service implementations XML format. This paper investigates the design of EXI processor targeted at highly resource constrained embedded devices found at the shop floor level. The EXI processor is proposed as an alternative to the XML parsers and serializers currently used in web service implementations. Among the results presented are a novel low level processor interface and measurements quantifying the gained efficiency compared to traditional XML-like interfaces. Reference open source implementation equipped with the new interface is also provided.